With the persistence provider, why there is still need of so much manual effort?

With persistence provider (EclipseLink), why there are still need so much manual effort in the following example shows how?
Done following manual effort necessary to the app using EclipseLink?
If the answer is Yes, the EclipseLink do for us?
The following content is from this link: http://wiki.eclipse.org/EclipseLink/Examples/JPA/JSF_Tutorial

_ Using JPA to implement Service

The main resource to manage the UI tutorial is org.eclipse.persistence.jpa.example.inventory.ui.InventoryManagerBean. It contains a reference to the following classes that use APP to implement the services provided by this application:

* org.eclipse.persistence.jpa.example.inventory.services.impl.ManagedOrderBean (implements org.eclipse.persistence.jpa.example.inventory.services.OrderService)
* org.eclipse.persistence.jpa.example.inventory.services.impl.ManagedInventoryBean (implements org.eclipse.persistence.jpa.example.inventory.services.InventoryService)

These two classes show how to use APP:

Acquisition of an entity manager factory
Create the entity
* Read an entity
* Update an entity
Delete the entity


Acquire a factory manager of the entity

The ManagedOrderBean and the ManagedInventoryBean use an instance of org.eclipse.persistence.jpa.example.inventory.services.impl.JPAResourceBean class assistance to get an instance of the entity manager factory for the default named persistence unit that we have defined in the file persistence.xml (see Configuration of the persistence unit). This example shows how the entity manager factory is acquired.

Acquisition of the managing body of the
public EntityManagerFactory getEMF (){
    if (emf == null){
        emf = Persistence.createEntityManagerFactory("default");
    }
    return emf;
}
Once acquired, the ManagedOrderBean and ManagedInventoryBean classes use the entity manager factory to obtain an entity manager to perform all basic persistence operations (create, read, update and delete).


Create an entity

This example shows how the ManagedOrderBean using the EntityManager to create a new entity of the order.

Creating a command in ManagedOrderBean
public void  createNewOrder(Order order){
    EntityManager em = jpaResourceBean.getEMF().createEntityManager();
    try{
        em.getTransaction().begin();
        em.persist(order);
        em.getTransaction().commit();
    }finally{
        em.close();
    }
}
...

Hello
If you are using an IDE like Eclipse 3.5, JDeveloper 11.1.1.1 or NetBeans 6.8M1 - EAR project assistants it will generate more all for you when you select the EclipseLink JPA default persistence provider.
Also, try the other tutorial JPA JSF - no based which shows the minimum get a compatible standard injected JEE EM using a JTA data source in a stateless session bean used by a customer of controller simple servlet. There are versions of this example for all major application servers using Oracle or Derby as a database.
http://wiki.Eclipse.org/EclipseLink/examples/JPA/WebLogic_Web_Tutorial
All tutorials EE and SE
http://wiki.Eclipse.org/EclipseLink/examples/JPA

All Tomcat base JPA tutorial will be a little more complex because Tomcat is not an EE real container - it only implements a web container with support for JTA datasource and lack of support for a managed container of JPA persistence context (so no injection of @PersistenceUnit EMF - it uses the class persistence bootstrap instead). That is why transactions and lifecycle States EM/EMF must be managed by the application and not transparently via default values annotation as a full EA server would be for you in GlassFish, JBoss, WebSphere, WebLogic and OC4J for example - tutorials for these EA servers are simpler.

Thank you
/Michael
http://www.EclipseLink.org

Tags: Fusion Middleware

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